Which champions were the most powerful and broken in League history?

It has been 2 years since I started to play League. That said, which were the most powerful, unbalanced, and broken champion in the history? I am speaking of champions that were so powerful that they were must bans, were clearly unbalanced and Riot had to fix them quickly for the sake of the game's balance.

The only 2 champions that I can recall to fit on those features are and .

If I'm not mistaken, Kassadin, before the removal of his silence, was banned in more than 95% of the draft pick matches. He was extremely unbalanced due to his silence, insane mobility, ability to ignore the frontline, absurd base damage AND scalings, and the fact that with his passive, he could counter many mages, although even AD champions could have a problem against him. This allowed him to win games alone. His early game was said to be weak, although it wasn't really weak, thanks to his silence and his ability to start with Flask + 3 pots and outsustain most champions.

As for Warwick, he is the only champion that I can think that can come close to how broken Kassadin was. At least during the patch 4.20, which introduced new jungle items, and made the jungle harder to clear due to some reasons, one of them being that you can now only start with Machete and 2 potions, instead of 4 potions like you used to be. Many champions were struggling with clearing the camps, but Warwick didn't had such problems at all, thanks to his incredible sustain, good base stats, and decent clearing speed. And due to how his ultimate interacted with Skirmisher's Sabre, as well as the Devourer enchantment, which was essentially a fully-stacked Feral Flare, Warwick was a force to be reckoned with, and like Kassadin, he could win games alone if you didn't banned him.